It has already been proposed to integrate into a security document, in practice including printed data intended to enable an identity check, a contactless electronic device, for example a microprocessor-based integrated circuit, intended to communicate with the external environment by means of an antenna, in such a manner as to enable contactless exchange of information between the document and an external control station. Data is typically exchanged at the initiative of the reader (the reader sends commands to which the contactless electronic device responds).
This kind of security document exchanges data that is richer in information than printed characters or even a photo, such as biometric data, and where appropriate verifies the compatibility of the printed data and the stored data, so as to detect any attempt to corrupt the printed data.
Nevertheless, this principle of contactless reading of data contained in the integrated circuit encounters entirely understandable resistance on the grounds that the data can be read unknown to the bearer, by systems that may be unauthorized.
Solutions for preventing such inopportune reading are already known.
For example, the document WO-2005/045754 identifies two reference positions of the document, for example “open” and “closed” positions, and provides for the data to be readable only in one or the other of those positions. To this end, the integrated circuit is connected to at least one element for coupling it to the outside environment which is capable, depending on the configuration of the security document, of exchanging information with the external environment or not. In the aforementioned document, the coupling element is an antenna produced on two sheets: depending on the geometry of this antenna and the instantaneous configuration of the document, the coupling element is operative or not. In a first embodiment, the antenna comprises turns each formed in part on each of said sheets, this antenna enabling exchange when the document is open (the turns have a maximum exchange section), whereas when the document is closed the halves of each turn are superposed so that they conjointly define a zero section, preventing any exchange with the external environment. A converse situation is obtained when the antenna is produced in the shape of the digit 8, with the antenna tracks crossing over on the fold line between the sheets: in this configuration, data can be exchanged only when the document is closed.
This kind of security document has the drawback of requiring a flexible electrical connection between the two sheets, which is costly to produce and gives rise to reliability problems.
Moreover, the security of the operation of this kind of document is not totally satisfactory in the presence of a reader station of high electromagnetic power.